A semiconductor device including a transistor and a non-volatile memory has established product lines, such as a complex programmable logic device (CPLD) and a field programmable gate array (FPGA), and has developed a large market because of its programmable features.
In a semiconductor device including a transistor and a non-volatile memory, for example, besides flash memory cells, high-voltage transistors for flash memory control and low-voltage transistors for high performance logic circuit are integrated on one semiconductor chip. In this case, unlike a single layer gate electrode structure of the high-voltage transistor or the low-voltage transistor, the flash memory cell has a stack gate electrode structure including a floating gate and a control gate laminated to each other.
In general, in the gate electrode of the flash memory cell having a stack gate structure, the floating gate is formed from a first layer conductive film, and the control gate is formed from a second layer conductive film. The gate electrode of a peripheral transistor having a single layer gate structure is formed from the second layer conductive film. In addition, between the floating gate and the control gate, an inter-gate insulating film is formed to insulate between the above two gates for capacitive coupling. This inter-gate insulating film is formed of a multilayer film (such as an ONO film) typically including a silicon oxide film and a silicon nitride film and is not formed in a peripheral transistor forming region. Hence, in a process of manufacturing a semiconductor device including a transistor and a non-volatile memory, before the second layer conductive film is deposited, removing the inter-gate insulating film provided in the peripheral transistor forming region may be performed.
In addition, as the non-volatile memory, besides the above flash memory, a non-volatile memory having a single layer gate structure in which an insulating film (such as an ONO film) is used as a charge storage layer has also been known. In the case of this non-volatile memory, before a gate electrode is formed, the charge storage layer provided in a peripheral transistor forming region may be removed. A high-voltage transistor used for controlling a non-volatile memory has been formed by a manufacturing process similar to that for the flash memory described above.
The prior arts regarding to the manufacturing method how to remove the a multilayer film from the semiconductor substrate are known in the patent documents as follows: Japanese Laid-open Patent Publication No. 02-244628 and M. Hayashi et al., “Deposition species from fluorocarbon film by Ar+ ion beam bombardment”, J. Vac. Sci. Technol. A, Vol. 18, No. 4, July/August 2000, pp. 1881 to 1886.